float PI = 3.14159265358979323846264;

vec4 brightnessContrast(vec4 color, float brightness, float contrast) 
{
	if (brightness < 0.0)  
	{
		color *= 1.0 + brightness;
	}
	else 
	{
		color += (1.0 - color) * brightness;
	}
	color = (color - 0.5) * (tan((contrast + 1.0) * PI / 4.0)) + 0.5;
	return color;
}
